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Pirtobrutinib is the First Reversible BTKi Approved in CLL / SLL

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Authored by Dr. Brian Koffman

On Dec. 1, 2023, pirtobrutinib received accelerated approval from the FDA for chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) patients who had failed two prior lines of therapy, including a BTK inhibitor (BTKi) and a BCL-2 inhibitor.

This approval was based on the BRUIN trial results, where the overall response rate was 72%, and the median duration of response was a little over a year. All responses were partial responses.

These are outstanding results in a difficult-to-treat population who now have an excellent approved option when their choices were limited before.

Adverse Events of Pirtobrutinib in CLL / SLL Patients

Pirtobrutinib was generally well tolerated, and the most common adverse events reported by patients included fatigue, bruising, cough, and musculoskeletal pain.

Serious infections were seen in almost 1/3, including fatal infections in 10% of patients.

Summary of Pirtobrutinib in CLL / SLL

Pirtobrutinib blocks the same pathway as the ibrutinibacalabrutinib, and zanubrutinib drugs that have revolutionized the care of CLL / SLL but does so differently than these three drugs. Pirtobrutinib works through reversible non-covalent binding. This means it will often continue to work even after the most common mutations that lead to resistance to ibrutinib, acalabrutinib, and zanubrutinib develop.

It is a welcome addition for patients who have “double refractory” disease, which is one of the most significant unmet needs for the CLL / SLL community.

Our work is not done. We still need more options and need to explore the use of pirtobrutinib as an earlier therapy for some patients. It makes sense to see how it works in less advanced diseases.

Here is the link to the official FDA Press Release: FDA grants accelerated approval to pirtobrutinib for chronic lymphocytic leukemia and small lymphocytic lymphoma.

Here is the Loxo@Lilly / Lilly press release.

Overall, this is excellent news for those with CLL / SLL, especially those running out of options.

Stay strong. We are all in this together.

Brian Koffman MDCM (retired) MS Ed (he, him, his)
Co-Founder, Executive VP, and Chief Medical Officer
CLL Society, Inc.